1. Technical Field
The present invention relates to an all-reflective optical system and, more particularly, to a wide field of view vehicle rear vision optical system.
2. Discussion
It has long been desirable when driving a vehicle to view traffic rearward of the driver. To accomplish rear viewing of traffic, the automotive industry has provided vehicles with rearview and sideview mirrors. Rearview mirrors are ordinarily mounted either on the windshield or the roof of the vehicle inside the passenger compartment of the vehicle. A ray trace of such a system is illustrated in FIG. 1. Rearview mirrors enable drivers to view rearward traffic in a rectangular field typically no greater than 6 degrees by 30 degrees. This field of view restriction is usually imposed by the size of the mirror or the size of the rear window in the vehicle. Sideview mirrors can increase this field of view somewhat. Generally, the sideview mirrors can be either planar or convex, and if convex, they operate at high magnifications significantly distorting real world spatial relationships.
The major disadvantage of these types of mirror systems is that, depending upon the vehicle, blind spots can exist to the driver. These blind spots are very dangerous and can cause a driver to glance in his mirror system and fail to see a vehicle in his blind spot. One attempt to eliminate blind spots is a large segmented planar mirror array within the passenger compartment across the roof of the vehicle. This type of array is unsatisfactory because of the discontinuous nature of the fields and the inherent limitations of viewing through the passenger compartment. Thus, it is desirous to have a rear vision optical system which substantially eliminates blind spots.